The present invention relates to filter coalescer cartridges, and more particularly to filter coalescer cartridges which perform well in the presence of surfactant-type additives in jet fuel.
Recently, new kerosene-based fuel has been developed for use in jet aircraft. The fuel is similar to previous jet fuels and contains an additional additive to improve the thermal stability of the fuel. Thermal stability of fuel used in fighter aircraft is critical and places increased heat transfer requirements on the fuel.
The additive has surfactant/detergency properties, which clean engine components as the fuel flows through the aircraft and engine fuel system. The additive functions in a manner similar to additives presently added to motor gasoline to clean fuel injectors.
Water removal from jet fuel is a critical requirement of any refueling filtration equipment. However, the presence of the new additive causes the removal of water from the fuel to be more difficult. Any water present in the fuel becomes more thoroughly emulsified as it is pumped through the ground fuel handling equipment. The emulsion is also more stable, resisting the removal of water with the conventional coalescence and settling process.
State of the art filter coalescer elements typically contain two major media sections: pleated media to primarily capture solid contaminant, and a surrounding cylinder of media to primarily coalesce the water to aid settling. The pleated media is usually wet-laid fiberglass papers, supported by either cellulose paper or synthetic media having adequate structure.
The pleated media also contributes to improve the coalescence of the water emulsion. The pleated media provides a critical aid to coalescence. The lower face velocity through the higher surface area of the pleated media is necessary to adequately coalesce water emulsions from the fuel. The pleated media is also functional to capture solid particulate contaminants. However, it has been found that such filter coalescer elements do not meet the new testing requirements.
Testing has shown that one media cannot adequately perform both functions. The upstream layer functions mainly to capture solid particles, but also starts the coalescing process. Due to more stringent particle capacity requirements in new test specifications, the first layer must have very high particle loading capacity (high solids/area of media).
The latest military fuel, JP8+100, contains additives which have strong surfactant and electrical properties. The current filter coalescer cartridges cannot adequately coalesce and separate water emulsions from the new fuel due to the emulsion stabilizing effect of the additives.
It is an object of the present invention to produce a new and improved filter coalescer element which exhibits good water coalescence and water separation.
Another object of the invention is to produce an improved filter coalescer element capable of effective water coalescence and water separation from hydrocarbon fluids and provide for increased solid particulate contaminant holding capacity.
The above, as well as other objects of the invention are typically achieved by a filter coalescer element for coalescing water emulsions in transient hydrocarbon fluids such as jet aircraft fuel and prevent the flow of particulate contaminants consisting of
a) a first layer of pleated filter media formed in an annular array of individual pleats to commence the water coalescence in the transient jet fuel and to remove particulate contaminants therefrom;
b) a second layer of pleated filter media formed in an annular array of individual pleats surrounding the first layer to coalesce the water in the transient fuel and to remove particulate contaminants therefrom;
c) a screen support layer surrounding the second layer of pleated filter media.